I've got a Flip Dictionary, a Thesaurus, my trusty Strunk&White, and I use the almighty GOOG(le) should I ever be unsure of the definition of a word. What does everyone else use? Is there some handy reference that I'm missing?

I'm not really concerned with style books...I see we've got two threads on those already. I want to know about word references and such.

I admit, I mostly stick to dictionary.com (and the app version from my iPod) for most of my look ups. I also use Google for any words my spellchecker chokes on. 9 times out of 10 it will suggest the correct spelling, even if I give it something a bit off the wall.

My window manager, Xfce, has a handy little taskbar app that will query a configurable list of dictionaries, thesauri, and other references -- everything from the Jargon File (a hacker lexicon) to Webster's Revised Unabridged Dictionary to Moby's Thesaurus, The CIA World Factbook, a legal dictionary, and dozens of other sources (you can also add custom ones).

Dictionary on Mac. Has a dictionary, thesaurus, and built-in formatted Wikipedia browser. I can switch between the definition of a word, the thesaurus, and the wikipedia entry for the word within immediately using keyboard-shortcuts.

I find the Oxford Collocations Dictionary very useful. It tells you which verbs tend to be used with a specific noun, which adverbs tend to be used with a verb, etc.

For non-native speakers this a real treasure which is unfortunately little known. Collocations are the kind of intuitions about a language which are very difficult to fully acquire, and they are hard to fathom from a normal dictionary.

I believe - though it's not really for me to say - that it also has a value for native speakers, both as useful form of a thesaurus - and, for creative writes, as a sort of dictionary of cliches to be used with care.